Composition and formulation comprising recombinant human iduronate-2-sulfatase and preparation method thereof

ABSTRACT

Disclosed are a composition comprising recombinant iduronate-2-sulfatase (IDS) and a method for treating Hunter syndrome. The glycosylation pattern and formylglycine content of the IDS composition are different from those of ELAPRASE® and have superior pharmaceutical efficacy and are safer than the conventional agent and thus can be effectively used for the therapy of Hunter syndrome.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/128,918 filed Dec. 23, 2013, which is a NationalStage of International Application No. PCT/KR2012/004734 filed Jun. 15,2012, claiming priority based on Korean Patent Application No.10-2012-0012718 filed Feb. 8, 2012 and claiming benefits from U.S.Provisional Patent Application No. 61/500,994 filed Jun. 24, 2011, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a composition for the treatment ofHunter syndrome, comprising recombinant human iduronate-2-sulfatase(hereinafter referred to as “IDS”), a formulation comprising the same,and a method for preparing the same.

More particularly, the composition for the treatment of Hunter syndromein accordance with the present invention comprises as an activeingredient IDS having an amino acid sequence represented by SEQ ID NO:1, wherein cysteine residue at position 59 in the IDS amino acidsequence of SEQ ID NO: 1 is converted to formylglycine (FGly:2-amino-3-oxopropionic acid) at a molar ratio of 65% or higher,preferably at a molar ratio of 75% or higher, and more preferably at amolar ratio of 80% or higher. In addition, the IDS contained in thecomposition for the treatment of Hunter syndrome containsmannose-6-phosphate in an amount of 2.0 to 4.0 moles per mole of IDS,preferably in an amount of from 2.3 to 3.5 moles, and more preferably inan amount of from 2.5 to 3.0 moles.

The method for preparing the composition for the treatment of Huntersyndrome in accordance with the present invention comprises:

(1) culturing a recombinant cell strain transformed with a gene encodingIDS represented by SEQ ID NO: 1 and obtaining the culture; and

(2) purifying the culture through anion exchange chromatography,hydrophobic chromatography, cation exchange chromatography, and affinitychromatography,

characterized in that the recombinant cell strain is cultured in thepresence of a hydrolysate and the cation exchange chromatography isperformed using an eluting buffer with a pH of 4.0 to 6.0.

Having advantages over conventional products in terms of safety andpharmaceutical efficacy, the therapeutic composition comprising IDS andthe formulation comprising the same can be effectively used to treatHunter syndrome.

BACKGROUND ART

Hunter syndrome or mucosaccharidosis type II is a lysosomal storagedisease (LSD) in which mucopolysaccharides, also known asglycosaminoglycans (GAG), are not broken down correctly and build up inthe body due to a deficiency of IDS. As GAG continues to buildupthroughout the cells of the body, various signs of Hunter syndromebecome more visible. Physical manifestations for some people with Huntersyndrome include distinct facial features and a large head.Representative among the symptoms of Hunter syndrome are an enlargedabdomen due to hepatomegaly or splenomegaly, deafness, valvular heartdisease, obstructive airway disease and sleep apnea. Also, major jointsmay be affected by Hunter syndrome, leading to joint stiffness andlimited motion. In some cases of Hunter syndrome, central nervous systeminvolvement leads to developmental delays and nervous system problems.Hunter syndrome is a known to occur at a rate of 1 in 162,000 and is agenetic disorder in the form of chromosome X-linked recessive and sogiven the great suffering to the family as well as the patient.

Various trials have been carried out thus regarding the treatment ofHunter syndrome, including bone marrow graft, enzyme replacement, andgene therapy. While bone marrow graft is able to stop most of thesymptoms, it is difficult to find an HLA (human leukocyte antigen) matchfor all patients. Further, a bone marrow graft is a major surgicaloperation accompanied by several adverse effects, including thepatient's life being put under high risk if the HLA is mismatched. Genetherapy for Hunter syndrome delivers a normal IDS gene into the bodywith the aid of a viral vector such as adenovirus or retrovirus or anon-viral vector. However, gene therapy remains an experimentaltechnique, and has not been clinically applied. As for the enzymereplacement treatment for Hunter syndrome, it administers externallyproduced IDS and has the advantage of being simple. However, enzymereplacement must be continuously carried out, which incurs a highexpense. ELAPRASE® (Shire Pharmaceuticals Group), produced usingrecombinant DNA technology, was approved by the FDA as an enzymereplacement treatment for Hunter syndrome. However, this drug is veryexpensive and suffers from the drawbacks of being poor in effect andsafety.

As described above, although various therapies for Hunter syndrome havebeen developed, there is still a pressing need for a new therapy andagent that exhibits high therapeutic efficacy with high safety.

DISCLOSURE Technical Problem

It is an object of the present invention to overcome the problemsencountered in the prior art and to provide a composition for thetherapy of Hunter syndrome, comprising recombinant IDS as an activeingredient, which guarantees high therapeutic efficacy and safety, asproduced by improved culturing and purifying processes, and aformulation comprising the same.

It is another object of the present invention to provide a method forpreparing the composition for the treatment of Hunter syndrome and theformulation comprising the same.

Technical Solution

To achieve the above object, the present invention provides acomposition for the therapy of Hunter syndrome, comprising as an activeingredient a recombinant IDS having an amino acid sequence representedby SEQ ID NO: 1, wherein cysteine residue at position 59 is converted toformylglycine (FGly) at a molar ratio of 65% or higher, preferably at amolar ratio of 75% or higher, and more preferably at a molar ratio of80% or higher.

IDS, herein also called iduronate-2-sulfatase or I2S, has a molecularsize of 56 kDa when isolated and purified from the human liver, kidneyor placenta (Bielicki, J. et al. (1990) Biochem, J., 271: 75˜86). IDS isexpressed as a monomeric protein of 550 amino acids and is secreted intothe medium as a mature active protein of 525 amino acids followingcleavage of the 25 amino acid signal peptide. The molecular weight ofIDS varies with glycosylation and was found to range from approximately60 to 90 kDa upon treatment with endoglycosidase F, as measured bySDS-PAGE.

IDS contains two disulfide bonds and eight N-linked glycosylation sitesand is produced as a glycoprotein after undergoing post-translationmodification in which the N-linked glycosylation sites are occupied bycomplex, hybrid and high mannose type oligosaccharide chains ineukaryotes. Once secreted into the culture medium, IDS may be used as adrug after going through typical isolation and purification processes.IDS may be in the form of glycoproteins with various glycosylationpatterns, depending on various factors, including, for example, IDSgenetic recombination, transformation (e.g., used cell lines), cultureand purification techniques.

In this invention, it is disclosed that the content ofmannose-6-phosphate (M6P) and the conversion ratio of Cys-59 to FGlyhave a great influence on the therapeutic efficacy and safety of IDS.The presence of mannose-6-phosphate (M6P) residues allows specificbinding of the enzyme to M6P receptors on the cell surface, leading tocellular internalization of the enzyme, targeting of lysosomes andsubsequent catabolism of accumulated GAG. Biological activity of IDS isalso dependent on a post-modification of the conserved cysteine(position 59) to formylglycine.

Unless stated otherwise, the term “IDS,” as used herein, means acarbohydrate-attached IDS protein, that is, a glycosylated IDS. The IDSof the present invention preferably has an amino acid sequence of SEQ IDNO: 1, but is not limited thereto. It should be apparent to those whohave ordinary knowledge in the art (hereinafter referred to as “ordinaryartisan”) that so long as it allows the IDS to retain the desiredactivity, any amino acid sequence in which mutations such as insertion,deletion and substitution occur on some amino acid residues of the aminoacid sequence of SEQ ID NO: 1 falls within the scope of the presentinvention.

As used herein, the term “glycosylation pattern” of IDS refers to theprofile of oligosaccharides bound to the eight glycosylation sites ofthe resulting IDS (e.g., glycosylation sites and kinds ofoligosaccharides).

In one embodiment, the IDS contained in the composition for the therapyof Hunter syndrome in accordance with the present invention has the sameamino acid sequence as is known (SEQ ID NO: 1), but has a differentglycosylation pattern and a different conversion ratio of cysteine atposition 59 to formyl glycine, as described above (refer to Examples 1-5and 1-6).

That is, the IDS used in the composition for the therapy of Huntersyndrome according to the present invention has an amino acid sequenceof SEQ ID NO: 1 with the conversion of cysteine at position 59 to formylglycine (FGly) at a molar ratio of 65% or higher, preferably at a molarratio of 75% or higher, and more preferably at a molar ratio of 80% orhigher, whereas the conversion ratio in ELAPRASE® is approximately 50%(Genet Med 2006:8(8):465-473). Formylglycine is known to be deeplyinvolved in the ability of IDS to degrade the substrate, that is theactivity of IDS. Thus, because the composition of the present inventionand the conventional agent ELAPRASE® are different, the composition andthe formulation according to the present invention can exhibit highertherapeutic efficacy for Hunter syndrome than can the conventional agentELAPRASE® because of a greater cytosine to formylglycine conversionratio at position 59 on the amino acid sequence of IDS.

In addition, the IDS used in the composition or the formulation for thetherapy of Hunter syndrome in accordance with the present inventioncontains mannose-6-phosphate in an amount of from 2.0 to 4.0 moles permole of IDS, preferably in an amount of from 2.3 to 3.5 moles and morepreferably in an amount of from 2.5 to 3.0 moles. M6P plays an importantrole in the cellular internalization of IDS and subsequent targeting tointracellular lysosomes. Thus, the formulation of the present inventioncomprising IDS with a high content of M6P guarantees the highperformance of the receptor-mediated uptake mechanism for this enzymeand targeting to lysosomes, thereby resulting in the effectivecatabolism of accumulated GAG.

The formulation for the therapy of Hunter syndrome comprising IDS inaccordance with the present invention can be prepared by formulating thecomposition of the present invention with a pharmaceutically acceptablecarrier into a suitable form.

As used herein, the term “pharmaceutically acceptable” carrier refers toa non-toxic, physiologically compatible vehicle for the activeingredient, which is suitable for ingestion by animals, without unduetoxicity, incompatibility, instability, irritation, allergic responseand the like.

The composition according to the present invention may be formulatedwith a suitable vehicle depending on the administration route taken. Theformulation according to the present invention may be administeredorally or parenterally but this is not limited to these. For parenteraladministration, a route selected from among transdermal, intranasal,intraperitoneal, intramuscular, subcutaneous or intravenous routes maybe taken.

For oral administration, the pharmaceutical composition may beformulated in combination with a suitable oral vehicle into powders,granules, tablets, pills, troches, capsules, liquids, gels, syrups,suspensions and wafers using a method known in the art. Examples of thesuitable vehicle useful in the formulation include sugars such aslactose, dextrose, sucrose, sorbitol, mannitol, xylitol, erythritol andmaltitol, starches such as corn starch, wheat starch, rice starch, andpotato starches, celluloses such as cellulose, methyl cellulose, sodiumcarboxymethyl cellulose, and hydroxypropyl methyl cellulose, and fillerssuch as gelatin and polyvinylpyrrolidone. Optionally, the formulationmay further comprise a disintegrant such as crosslinkedpolyvinylpyrrolidone, agar, alginic acid or sodium alginate. Inaddition, an anti-agglomerating agent, a lubricant, a wetting agent, afragrant, an emulsifier, and a preservative may be further employed.

Also, the composition of the present invention may be formulated incombination with a parenteral vehicle into a parenteral dosage form suchas an injectable preparation, a transdermal preparation or an intranasalinhalation using a method well known in the art. For use in injection,the formulation must be sterilized and protected from contamination withmicroorganisms such as bacteria and fungi. Examples of the vehiclesuitable for injection may include, but are not limited to, water,ethanol, polyol (e.g., glycerol, propylene glycol, liquid polyethyleneglycol, etc.), combinations thereof, and/or a vegetable oil-containingsolvent or dispersion medium. More preferably, the vehicle may be anisotonic solution such as Hank's solution, a Ringer's solution,triethanol amine-containing PBS (phosphate buffered saline) orinjectable sterile water, 10% ethanol, 40% propylene glycol and 5%dextrose. In order to protect the injectable preparation from microbialcontamination, it may further comprise an antibacterial and antifungalagent such as paraben, chlorobutanol, phenol, sorbic acid, thimerosal,etc. Also, the injectable preparations may further comprise, in mostcases, an isotonic agent such as sugar or sodium chloride. Theseformulations are disclosed in a document well known in thepharmaceutical field (Remington's Pharmaceutical Science, 15^(th)Edition, 1975, Mack Publishing Company, Easton, Pa.). As concernsinhalation, the formulation according to the present invention may bedelivered conveniently in the form of an aerosol spray from a compressedpack or sprayer using a suitable propellant, such asdichlorofluoromethane, trichlorofluoromethane,dichlorotetrafluoroethane, carbon dioxide or a suitable gas. In the caseof compressed aerosol, the unit size of a dose may be determined by avalve for delivering a metered amount. For example, gelatin capsules andcartridges for use in an inhaler or insufflator can be formulatedcontaining a powder mix of the compound and a suitable powder base suchas lactose or starch for these systems.

Other suitable pharmaceutical vehicles are described in Remington'sPharmaceutical Sciences, 19^(th) ed., Mack Publishing Company, Easton,Pa., 1995.

Moreover, the formulation according to the present invention may furthercomprise one or more buffers (e.g., saline or PBS), carbohydrates (e.g.,glucose, mannose, sucrose or dextran), stabilizers (sodium hydrogensulfite, sodium sulfite or ascorbic acid), anti-oxidants,bacteriostatics, chelating agents (e.g., EDTA or glutathione), adjuvants(e.g., aluminum hydroxide), suspending agents, thickeners and/orpreservatives (benzalkonium chloride, methyl- or propyl-paraben andchlorobutanol).

Also, the composition of the present invention may be formulated into adosage form that allows the rapid, sustained or delayed release of theactive ingredient after being administered into mammals. An effectiveamount of the formulation thus prepared may be administered via avariety of routes including oral, transdermal, subcutaneous, intravenousand intramuscular routes. The term “effective amount,” as used hereinrefers to an amount of IDS that allows tracing the diagnostic ortherapeutic effect to take place when administered into a patient. Thedose of the formulation according to the present invention may varydepending on various factors including, the route of administration, thetype of subject to be treated, the type of disease to be treated, theadministration route, the severity of the illness, and the patient'sage, gender, weight, condition, and health state. The formulationcomprising IDS according to the present invention may be used at a doseof from 0.1 to 10 mg/kg and preferably at a dose of from 0.5 to 1.0mg/kg per dosage.

The method for preparing the therapeutic composition in accordance withthe present invention comprises:

(1) culturing a recombinant cell strain transformed with a gene encodingIDS represented by SEQ ID NO: 1 and obtaining the culture; and

(2) purifying the culture through anion exchange chromatography,hydrophobic chromatography, cation exchange chromatography, and affinitychromatography,

wherein, the recombinant cell strain is cultured in the presence of ahydrolysate and the cation exchange chromatography is performed using aneluting buffer with a pH of 4.0 to 6.0.

More particularly, the method for preparing the therapeutic compositionin accordance with the present invention comprises:

(1) transforming a host cell with an expression vector carrying a IDSgene to obtain a recombinant cell strain;

(2) culturing the recombinant cell strain in the presence of ahydrolysate in a serum-free medium and obtaining the culture;

(3) purifying IDS from the culture through anion exchangechromatography, hydrophobic chromatography, cation exchangechromatography and affinity chromatography, said cation exchangechromatography being performed using an eluting buffer ranging in a pHfrom 4.0 to 6.0; and

(4) combining the purified IDS with a pharmaceutically acceptablecarrier.

In the method, step (1) is directed to establishing a recombinant cellstrain by introducing an expression vector carrying an IDS gene into ahost cell. The amino acid sequence of IDS and a gene encoding IDS areknown in the art. A gene that codes for the IDS having the amino acidsequence of SEQ ID NO: 1 is preferred, but is not provided as a limitingexample. If an amino acid sequence retains the activity of IDS sought tobe brought about by the purpose of the present invention, althoughmutated by insertion, deletion and/or substitution of some amino acidresidues on the amino acid sequence of SEQ ID NO: 1, its gene may beused in the present invention. The expression vector carrying the genemay be constructed using a typical method known in the art. In addition,the expression vector may contain a marker gene which allows theintroduction of the gene to be identified. Examples of the marker geneinclude a dihydrofolate reductase gene (dhfr), but are not limitedthereto. Preferable is a pJK-dhfr-Or2-IDS vector (FIG. 2).

The host cells available for step (1) may be animal cells and theirexamples include, but are not limited to, Chinese hamster ovary (CHO)cells, human embryonic kidney (HEK) cells, baby hamster kidney (BHK)cells, monkey kidney cell 7 (COS7), and NSO cells, with a preference forCHO cells. CHO cell lines are one of the most widely used in theproduction of biomedical products thanks to their high cell growth ratesand productivity, ease of genetic manipulation, rapid proliferation inlarge-scale suspension cultures and high adaptation to protein-freemedia. The transformation in step (1) may be carried out according to aprotocol known in the art.

In the method, step (2) is directed to culturing the recombinant cellstrain anchoring the IDS expression vector therein in a serum-freemedium. The culturing may be carried out in a medium and underconditions optimized for the kind of host cell. Preferred is aserum-free medium. Being free of sera (e.g., bovine sera), such mediaavoid the likelihood of inducing the side effects or risks associatedwith sera.

In one embodiment of the present invention, the culturing of therecombinant cell strain transformed with an IDS expression vector may befurther scaled up. For example, the recombinant cell strain of thepresent invention may be cultured in a shaker flask and then scaled upto hundreds to thousands of liters in a bioreactor. The culturing stepis carried out in the presence of a hydrolysate, which has an importantinfluence on the determination of formylglycine content. Preferably, thehydrolysate is added in such an amount as to form a final concentrationof 0.1˜10.0 g/L. The hydrolysate useful in the present invention may bethose obtained by hydrolyzing an animal or plant material. Moreparticularly, the hydrolysate may be obtained by hydrolyzing at leastone selected from the group consisting of, but not limited to, soybean,potato, wheat germ, and yeast.

In the method, step (3) is directed to the purification of IDS from thecell culture through anion exchange chromatography, hydrophobicchromatography, cation exchange chromatography, and affinitychromatography.

Preferably, the four chromatographic processes may be performed in thatorder. However, it should be obvious to an ordinary artisan that theorder may be changed if necessary. Together with the order of thechromatographic processes, the resins and the pH values of the elutingbuffers are important in determining the glycosylation pattern andformylglycine content of IDS.

Anion exchange chromatography is intended to remove dyes and variousimpurities from the cell culture and is performed on a column filledwith Q Sepharose® resins using an eluting buffer with a pH of from 5.5to 7.5.

Hydrophobic chromatography is intended to remove the dyes and impuritiesthat remain after anion exchange chromatography. It is performed on acolumn filled with phenyl Sepharose® resins, using an eluting buffer ata pH of from 5.0 to 7.0.

Cation exchange chromatography is intended to select high theformylglycine content and remove remaining impurities. It is performedon a column filled with cation exchange resins, using an eluting bufferwith a pH of from 4.0 to 6.0. Examples of the cation exchange resinsuseful in the present invention may include CM Sepharose Fast Flow, SPSepharose Fast Flow, S Sepharose Fast Flow and Capto MMC, all from GEHealthcare, but are not limited thereto. Preferably, the eluting bufferranges in pH from 4.0 to 6.0.

Affinity chromatography is intended to remove the glycerol used in thecation exchange chromatography and concentrate the volume of theeluates. It is performed on a column filled with Blue Sepharose™ resins,using an eluting buffer with a pH of from 6.0 to 8.0.

The conditions of each type of chromatography may be optimally modifiedby the ordinary artisan. With regard to concrete chromatographyconditions, reference may be made to Example 1-5 described below.

The method for preparing the composition comprising IDS as an activeingredient in accordance with the present invention may further compriseinactivating viruses that may be incorporated into the composition. Theinactivation may be conducted in various ways, and preferably by holdingthe culture at pH 3.0˜4.0 or under a high pH condition for apredetermined time. The inactivating process may be achieved during thepurification process, preferably during the chromatography, and morepreferably between the hydrophobic chromatography and the cationexchange chromatography.

After the chromatographic processes, the active fraction thus obtainedmay be concentrated and filtered to afford IDS which can be used as theactive ingredient of the pharmaceutical composition.

The composition may be mixed with a pharmaceutically acceptable carrierand formulated into a suitable dosage form.

The composition comprising the IDS, prepared by the method according tothe present invention, has advantages over conventional IDS compositionsas follows 1) it exerts higher pharmaceutical efficacy thanks to ahigher formylglycine content, 2) it can more effectively catabolize GAGaccumulated within lysosomes, 3) it is free of animal-derived serum andthus safe, and 4) it is safe and efficacious thanks to its purity of99.9% or higher.

Advantageous Effects

The composition comprising the recombinant IDS and the formulationcomprising the same in accordance with the present invention aresuperior in pharmaceutical efficacy and safety to the conventional agentELAPRASE® and thus can be effectively used for the therapy of Huntersyndrome.

DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a scheme for constructing thepJK-dhfr-IDS-S1 vector used to construct an IDS expression vector.

FIG. 2 is a view illustrating a scheme for constructing the IDSexpression vector pJK-dhfr-Or2-IDS from the pJK-dhfr-IDS-S1 of FIG. 1.

FIG. 3 is a flow chart illustrating the isolation and purification ofIDS from transformed CHO-DG44.

FIG. 4 is a photograph showing an SDS-PAGE result of IDS for analyzingthe N-terminal sequence where a marker was run on lane M, glycosylatedIDS on lane 1, PNGase F on lane 2, and deglycosylated IDS on lane 3.

FIG. 5 is a flow chart illustrating the process of analyzing the aminoacid sequence of IDS.

FIG. 6 is a view showing the amino acid sequence of the IDS of thepresent invention as analyzed by MALDI-MS/MS and LC-ESI-MS/MS.

FIG. 7 is an RP-HPLC chromatogram of non-reduced and reduced IDS samplesshowing the position of disulfide bonds in IDS.

FIG. 8 is a view showing the positions of disulfide bonds in the IDS ofthe present invention as analyzed by MALDI-MS.

FIG. 9 is a view showing the positions of disulfide bonds in the IDS ofthe present invention as analyzed by MALDI-MS/MS.

FIG. 10 is a view indicating the positions of disulfide bonds in the IDSof the present invention, obtained through MALDI-MS/MS.

FIG. 11 is a photograph showing IDS run by SDS-PAGE after treatment withvarious glycoside hydrolase enzymes to examine the glycosylation of theIDS of the present invention.

FIG. 12 is of HPAEC-PAD chromatograms showing the content ofmannose-6-phosphate in the IDS of the present invention.

FIG. 13 is a size exclusion chromatogram showing the purity of the IDSof the present invention.

FIG. 14 is an ion chromatogram showing the catalytic activity of the IDSof the present invention on a natural substrate.

FIG. 15 is Lineweaver-Burk plot showing ratios of cellular uptakeamounts of IDS relative to amount of IDS added to normal fibroblastcells.

FIG. 16 is a graph showing the amount of the IDS of the presentinvention internalized into normal human fibroblast cells and the cellsof patients suffering from Hunter syndrome.

FIG. 17 is a view showing measurements of the formylglycine content inthe IDS of the present invention.

FIG. 18 is a view showing IEF (isoelectric focusing) points of the IDSof the present invention before and after cation exchange chromatographywherein M is run on M lane, a loaded sample for cation exchangechromatography on lane 1, an eluate of cation exchange chromatography onlane 2, and a regeneration solution after cation exchange chromatographyon lane 3.

MODE FOR INVENTION

A better understanding of the present invention may be obtained throughthe following examples which are set forth to illustrate, but are not tobe construed as limiting the present invention.

EXAMPLE 1 Preparation of IDS

<1-1> Gene Acquisition

Peripheral blood mononuclear cells (PBMC) were isolated from human bloodas described previously [S. Beckebaum et al., Immunology, 2003,109:487-495]. Total RNA was extracted from the PBMC according to aprotocol described previously [M. J. Holland et al., Clin. Exp.Immunol., 1996, 105:429-435]. In order to construct a cDNA library fromthe total RNA, single-stranded cDNA was synthesized using oligo-(dT)primer with the aid of a single-strand synthesis kit (Boehringermannheim). In this regard, DEPC-treated distilled water was added to aneppendorf tube containing 1 μg of the total RNA so as to form a finalvolume of 12.5 μL. Then, 1 μL of a 20 pmol oligo(dT) primer was added tothe tube, followed by incubation at 70° C. for 2 min and cooling. Tothis reaction mixture were added 4 μL of a reaction buffer, 1 μL ofdNTP, 1 μL of an RNase inhibitor, and 1 μL of reverse transcriptasewhich were then reacted at 42° C. for one hour to synthesize singlestranded cDNA. PCR was performed on the cDNA as a template in thepresence of primers of SEQ ID NOS: 2 to 4 to amplify a human IDS gene.In this context, each primer was designed to contain a restrictionenzyme recognition site for use in gene cloning.

<1-2> Construction of Expression Vector

A. Construction of pJK-dhfr-IDS-S1 Vector

A light chain signal sequence of an antibody (derived from a part of thehuman IgG light chain) as a non-coding sequence was introduced into the5′-terminus of the IDS gene acquired by Example <1-1> before PCR. Afterthe PCR product obtained thereby was run on gel by electrophoresis, thehuman IDS gene was isolated using a gel extraction kit. The isolated IDSgene and the pJK-dhfr-Or2 vector (Aprogen) were digested with EcoRV andApaI and ligated to each other at 16° C. for 20 hours. The recombinantvector thus constructed was transformed into E. coli (DH5α) which wasthen spread over an LB plate containing 50 μg/mL ampicillin andincubated overnight. Colonies grown on the plates were selected andcultured so as to isolate the plasmid therefrom (FIG. 1).

B. Construction of Recombinant Human IDS Expression Plasmid

In order to change the non-coding sequence of the plasmid constructedabove to a signal sequence, the recombinant human IDS was subcloned to apJK-dhfr-or2 vector. To this end, the pJK-dhfr-IDS-S1 vector wasdigested with EcoRV and ApaI to give a partial IDS gene (1233 bp) whichwas then inserted into the pJK-dhfr-Or2 vector previously treated withthe same restriction enzymes, to construct a pJK-dhfr-IDS-S2 vector. Inorder to introduce a non-coding sequence and a signal sequence to the5′-terminus, an IDS N1 forward primer (SEQ ID NO: 5) and an IDS 4reverse primer (SEQ ID NO: 7) were used for PCR with the pJK-dhfr-IDS-S1vector serving as a template. After starting at 94° C. for 5 min, PCRwas performed with 30 cycles of 94° C. for 1 min, 55° C. for 30 sec and72° C. for 40 sec and finished by extension at 72° C. for 10 min.

The PCR amplification afforded a partial IDS gene that was 448 bp. Thisgene was used as a template for the PCR which was performed again in thepresence of an IDS N2 forward primer (SEQ ID NO: 6) and an IDS 4 reverseprimer (SEQ ID NO: 7) under the same conditions as described above. Thisresulted in the synthesis of a DNA fragment 476 bp long.

Subsequently, the pJK-dhfr-IDS-S2 vector and the recombinant human IDSgene fragment (476 bp) were separately digested with EcoRV. The digestswere separated on gel by electrophoresis to obtain the vector and the476 bp-long IDS fragment. These vector and insert were ligated at 16° C.for 12 hours in the presence of T4 DNA ligase to constructpJK-dhfr-Or2-IDS plasmid. These procedures are illustrated in FIG. 2.

To confirm the construction of the IDS expression plasmid, DH5α wastransformed with pJK-dhfr-Or2-IDS and cultured for 24 hours on an LBplate containing ampicillin (50 μg/mL). From the colonies thus formed, aplasmid was isolated and digested to measure the size of the insert.Also, base sequencing was conducted using a T7 primer (SEQ ID NO: 8).

<1-3> Selection of Recombinant Human IDS Expression Strain

A. Transfection of CHO-DG44

CHO-DG44 was used as a host cell for expressing the IDS of the presentinvention. The mutant Chinese hamster ovary cell CHO-DG44 carries adouble deletion for the endogenous dhfr (dihydrofolate reductase) genewhich encodes DHFR enzyme. The DHFR enzyme is involved in the conversionof folate through dihydrofolate (FH2) into tetrahydrofolate (FH4) whichis involved in the de novo synthesis of nucleic acids. The level of dhfrin the cells is dependent on the concentration of MTX. MTX, which isstructurally similar to folic acid, a substrate of DHFR, competes withfolic acid for binding dihydrofolate reductase, so that mostdihydrofolate reductase loses its activity in the presence of MTX.Hence, if cells do not amplify a sufficient amount of dhfr, they diebecause they cannot synthesize nucleic acids necessary for their life.In contrast, if the amplification is sufficient, the cells can surviveunder a high concentration of MTX because they are relatively abundantin dhfr. This system may be applied to animal cells to select atransfected cell line which can amplify the dhfr gene and thus astructural gene of interest.

To this end, a dhfr gene was introduced as an amplifiable marker intothe IDS expression vector pJK-dhfr-Or2-IDS, constructed in Example 1-2,and gene amplification was conducted using MTX and the dhfr gene.

In this regard, the DG44 cell line (obtained from Dr. Chaisin, ColumbiaUniversity) was suspended in 10 mL of DMEM/F12 (supplemented withnucleotides and nucleosides, and 10% fetal bovine serum (FBS)) andharvested by spinning at 1000 rpm for 5 min. The cells were inoculatedinto 50 mL of a culture medium in a T-175 flask and incubated at 37±1°C. in a 5±1% CO₂ incubator. One day before transfection, the culturemedium for DG44 cells was removed from the T-175 flask and the cellswere washed twice with PBS and detached by trypsinization. Then, theywere seeded at a density of 5×10⁵ cells into a T-25 flask and culturedat 37±1° C. for 24 hours in a 5±1% CO₂ incubator. Bacterial or fungalcontamination was examined under an optical microscope while PCR-ELISAwas performed to examine whether the cells were contaminated withmycoplasma.

The germ-free DG-44 cells were transfected with the IDS expressionvector pJK-dhfr-Or2-IDS, constructed in Example 1-2, using aLipofectamine kit. In this regard, 5 μg of the expression vector and 50μL of Lipofectamine were separately diluted in 800 μL of Opti-MEM I,mixed carefully so as not to form bubbles, and left at room temperaturefor 15 min. Meanwhile, DG44 cells were washed once with sterile PBS andthree times with Opti-MEM I. To the DG44 cells were carefully added theDNA-lipofectamine mixture and then 6.4 mL of Opti-MEM before incubationat 37±1° C. for 5 hours in a 5±1% CO₂ incubator. Thereafter, theincubation was conducted for an additional 48 hours in the mediumsupplemented with 8 mL of DMEM/F12 and 1.6 mL of FBS to promote therecovery of cell membranes and the growth of cells.

B. Selection of Geneticin (G418)-resistant Cell Strain

The cultured cells were detached with 0.25% trypsin, counted, and seededat a density of 5×10³ cells/well into 96-well plates containing 100 μLof MEM-alpha medium (supplemented with 10% dialyzed FBS and 550 μg/mLG418) per well. Next day, the same medium was added in an amount of 100μL/well and the cells were cultured for 2-3 weeks to form colonies. Whenthe cells grew to 50% confluency, the medium was replaced with a freshone. After maintenance for 3 days, the culture media were collected forenzyme analysis.

The medium was replaced with 200 μL of a fresh medium every three days.On day 3˜4 after culturing, non-transfected cells, that is, cells thatwere not resistant to geneticin started to detach from the bottom of the96-well plates when observed with an optical microscope. The selectedclones were cultured while being sequentially transferred from the96-well plates to 24-well plates, 6-well plates and 100-mm dishes in theorder. When the cells grew to 80˜90% confluency in 100-mm dishes, theexpression level was measured again. The cells were detached with 0.25%trypsin, counted and plated at a density of 5×10⁵ cells/well/3 mL into6-well plates, maintained for 3 days and counted. The expression levelof the protein was quantitatively analyzed. According to the analysisresults, 15 clones were selected.

C. Selection of IDS Expression Strain with High Expression Capacity

The 15 selected clones were cultured at an increased concentration ofMTX to select cell strains in which IDS was amplified.

In this context, the cells were inoculated at a density of 1×10⁶cells/100 mm dish/10 mL of a medium containing MTX and cultured to80˜90% confluency. One tenth of the volume of the cell culture wasinoculated again into 100 mm dish/10 mL. This sub-culturing process wasrepeated twice. The cells were allowed to undergo at least threepassages so that they were sufficiently adapted to increased MTXconcentrations. The concentration of MTX was increased, from 5 nM forthe clones selected after conducting an analysis for the first threedays, to 20 nM. In each step, the clones adapted to the increased MTXconcentration were cultured for three days to measure cell growth rates.IDS expression levels were measured to select cell strains in which theamplification of the IDS gene took place, that is, cell strains in whichthe recombinant IDS was expressed at a high rate. Of the selected cellstrains, NI4 was used in subsequent experiments because it had thehighest expression level.

D. Selection of Single Strain by Limiting Dilution There was thepossibility that the strain NI4 might have become mixed with otherstrains. Hence, the strain was separated into a single strain. The N14clones which survived 20 nM MTX were subcloned through limiting dilutionso as to select a desired cell strain.

First, NI4 was inoculated at a density of 0.5 cells/well into IMDMmedium (Gibco BRL, Cat#12200) in 96-well plates and cultured with themedium replenished every three days. On day three, the plates wereobserved under a microscope to exclude the wells in which two or morecolonies had been formed per well. The wells in which only one colonyhad formed per well were selected and continued to be cultured. Afterculturing for 15 days, the cells were sub-cultured to 96-well plates andwhen cells had grown to 90% confluency, the medium was freshlyreplenished.

A total of 263 single strains were identified from the N14 strain. Ofthem, strain S46 was found to have the highest IDS activity and namedNI4-S46.

<1-4> Cell Culture

A. Shaker Flask Culture

The NI4-S46 strain was cultured on a large scale to produce the IDS ofthe present invention. The strain was inoculated into an EX-cell 302serum-free medium (containing glutamine, dextran sulfate, and pluronicF-68) in 125 mL culture flasks and cultured at 37±1° C. in a 5±1% CO₂incubator. Subsequently, the cells were passaged at a ratio of 1:5˜1:8every two to three days using shaker flasks. Upon the passage, theculture volume was gradually increased to approximately 2,400 mL. Inmany shaker flasks, the cells were cultured to a level sufficient to beinoculated into a fermentor.

B. Culture in 30 L Fermentor (Working Volume 20 L)

When the density of the cells in the shaker flasks reached 1.3×10⁶cells/mL, they were inoculated into a 30 L fermentor. During cellculturing, the culture conditions were kept at a dissolved oxygencontent of 10% or higher, a culture temperature of 37±1° C. and a pH of7.0±0.2. If necessary, cell samples were taken and observed under amicroscope. The cell culture was examined to analyze cell count, cellviability, pH, glucose concentration and glutamine concentration. On thebasis of the analysis results, when it was decided that the cells weresufficiently grown, the cells were inoculated into a 150 L fermentor.

C. Culture in 150 L Fermentor (Working Volume 100 L)

When the cells in a 30 L fermentor reached a density of 0.9×10⁶ cells/mLor higher, they were inoculated into a 150 L fermentor. During cellculturing, the culture condition was kept at a dissolved oxygen contentof 10% or higher, a culture temperature of 37±1° C. and a pH of 7.0±0.2.If necessary, cell samples were taken and observed under a microscope.The cell culture was examined to analyze cell count, cell viability, pH,glucose concentration and glutamine concentration. On the basis of theanalysis results, when it was decided that the cells were sufficientlygrown, the cells were inoculated into a 650 L fermentor.

D. Culture in 650 L Fermentor (working volume 500 L) When the cells in a150 L fermentor reached a density of 0.9×10⁶ cells/mL or higher, theywere inoculated into a 650 L fermentor. During cell culturing, theculture condition was kept at a dissolved oxygen content of 10% orhigher, a culture temperature of 34±1° C. and a pH of 6.9±0.2 for threedays and then, at a culture temperature of 32±1° C. and a pH of 6.9±0.2.If necessary, cell samples were taken and observed under a microscope toanalyze cell counts, cell viability, pH, glucose concentrations andglutamine concentrations. Depending on the analysis result, glucose andglutamine concentrations were adjusted to continue cell growth. Duringthe fermentation, a hydrolysate was added to increase the formylglycineconversion.

<1-5> Purification of IDS IDS was isolated from the cell culture using aseries of the following four chromatographic processes.

A. Harvest and Filtration of Culture Medium

When the cell viability remained in the range of 80˜85% 10 days afterinoculation into the 650 L fermentor, culturing was stopped. The cellswere harvested from the culture using the Millipore POD filter systemand D0HC filter (Millipore) at a pressure of 0.9 bar or less. After thecells were removed, the supernatant was filtered through a pre-filter(Millipore, 0.5±0.2 μm) and a 0.45+0.2 μm filter and recovered in adisposable sterile vinyl bag. The harvested culture solution was storedat 2˜8° C.

B. Concentration and Diafiltration

The filtrate recovered in A was about 10-fold concentrated using anultrafiltration system (Tangential Flow Filtration Membrane System). Themembrane (cutoff: 30K, Pall) installed inside the ultrafiltration systemwas washed with WFI (water for injection) at a flow rate of 20˜25 L/minand then equilibrated with a buffer (pH 7.0˜8.0) containing 20 mM sodiumphosphate (sodium dihydrogen phosphate monohydrate and sodium hydrogenphosphate heptahydrate). After equilibration, the filtrate was fed intothe membrane while recovering the fractions that did not pass themembrane. Once the recovered volume became about 1/10 of the initialvolume of the filtrate, the concentration procedure was stopped. Thebuffer was consecutively exchanged in a volume three to four times aslarge as that of the concentrate. If the conductivity and the pH fellwithin the criteria, the process was stopped. [criteria—conductivity:≦5.0 mS/cm, pH 7.0˜8.0].

C. Anion Exchange Chromatography

To remove dyes and various impurities from the concentrate recovered inB, anion exchange chromatography was conducted on a column (GEHealthcare) filled with Q Sepharose resins (GE Healthcare). The columnwas equilibrated with equilibrium buffer (pH 7.0˜8.0) containing 20 mMsodium phosphate (sodium dihydrogen phosphate monohydrate and sodiumhydrogen phosphate heptahydrate). The concentrate obtained in B wasfiltered through a 0.45±0.2 μm filter (Sartorius) and loaded at a flowvelocity of 100˜120 cm/h into the equilibrated column. After the loadingwas completed, the column was primarily washed with the equilibriumbuffer and then with washing buffer (pH 5.5˜7.5) containing sodiumchloride. Subsequently, a target protein was eluted with an elutingbuffer (pH 5.5˜7.5) containing sodium chloride.

D. Hydrophobic Chromatography

To remove the dyes and impurities that remained after anion exchangechromatography, hydrophobic chromatography was performed on a column (GEHealthcare) filled with phenyl Sepharose resins (GE Healthcare). Thecolumn was equilibrated with equilibrium buffer (pH 5.0˜7.0) containingsodium chloride. The eluate obtained in C was filtered through a0.45±0.2 μm filter (Sartorius) and loaded at a flow velocity of 70˜100cm/h into the equilibrated column. After the loading was completed, thecolumn was washed with the equilibrium buffer. Subsequently, a targetprotein was eluted with an eluting buffer (pH 5.0˜7.0) containingglycerol.

E. Inactivation of Virus by Low pH

Viruses that may be derived from host cells or any material used in theprocesses carried out were inactivated by a low pH condition. In thisregard, the eluate obtained in D was maintained for 2 hours at a pH3.0˜4.0 to which its acidity was adjusted with 25% acetic acid.Thereafter, the pH of the eluate was increased to 4.0˜5.0 using 0.5 Msodium hydroxide for use in the next process. The inactivation by low pHwas conducted at 12±2° C.

F. Cation Exchange Chromatography

IDS is glycoprotein with oligosaccharides, and exists as an isomer thathas a different isoelectric point according to the content of sialicacid at the end of the Glycan chain. As oligosaccharides with a negativecharge, sialic acid shows a difference in terms of the degree of bindingto cation exchange resin according to the content of sialic acid. Usingthis characterization, cation exchange chromatography was conducted toobtain IDS showing high activity (a high content of formylglycine) witha high content of sialic acid and to remove other impurities [Productimpurity (Aggregated IDS, processed IDS), process impurity (Host Cellprotein)]. In detail, a column filled with cation exchange Capto™ MMCresins (GE Healthcare) was equilibrated with glycerol-addedequilibration buffer (pH 4.0˜5.0). The inactivated eluate obtained in Ewas filtered through a 0.45±0.2 μm filter (Sartorius) and loaded at aflow velocity of 100˜120 cm/h onto the equilibrated column.Subsequently, the column was washed with the equilibration buffer,followed by elution with glycerol-added eluting buffer (pH 4.0˜6.0) togive IDS with a high sialic acid content (isoelectric point 3.5 orless), high activity (formylglycine content: 80±15%) and high purity(SE-HPLC, 98% or higher).

G. Affinity Chromatography

Affinity chromatography (Blue Sepharose, GE Healthcare) was conducted toremove the glycerol used in the cation exchange chromatography and toreduce the volume of the eluate. The eluate obtained in F was filteredthrough a 0.45±0.2 μm filter (Sartorius) and loaded at a flow velocityof 100˜120 cm/h onto a Blue Sepharose resin-filled column (GEHealthcare) that was previously equilibrated with glycerol-addedequilibration buffer (pH 4.5˜5.5). After completion of the loading, thecolumn was washed with washing buffer (pH 4.5˜5.5) and the targetprotein was eluted with eluting buffer (pH 6.0˜8.0).

H. Concentration and Buffer Exchange

An ultrafiltration system (Tangential Flow Filtration Membrane System)was used to adjust the protein concentration of the eluate obtained in Gand to exchange the buffer of the purified protein with formulationbuffer. The membrane (cutoff: 10K, Pall) installed inside theultrafiltration system was washed with WFI (water for injection) at aflow rate of 450˜650 mL/min and then equilibrated with a formulationbuffer (2.25 g/L sodium dihydrogen phosphate monohydrate, 0.99 g/Lsodium hydrogen phosphate heptahydrate, 8 g/L sodium chloride, pH6.0˜7.0) without polysorbate 20, followed by concentrating the targetprotein. The buffer was consecutively exchanged in a volume three tofour times as large as that of the concentrate. If the conductivity andthe pH fell within the criteria, the process was stopped.[criteria—conductivity: 15.0±3.0 mS/cm, pH 6.0˜7.0]. Adjust the contentof the concentrated solution to 4.0±0.5 mg/mL.

I. Nanofiltration

Using a nano filter (NFP, Millipore), nano filtration was performed toremove viruses that might have come from the host cells or any of thematerials used. Integrity test for filter is performed after washing thenano filter with water for injection. Once the integrity test waspassed, the nanofilter was equilibrated with 1 L of formulation buffer(2.25 g/L sodium dihydrogen phosphate monohydrate, 0.99 g/L sodiumhydrogen phosphate, 8 g/L sodium chloride, pH 6.0˜7.0) withoutpolysorbate 20. After completion of equilibration, the concentrateobtained in H was passed through the filter at a pressure of about 2 barto produce a nano-filtrate. After filtration was completed, the filterwas washed with the formulation buffer (post wash solution). Aftercombining the nano filtration solution and the post wash solution,protein content is measured.

J. Drug Substance

The protein concentration of the filtrate obtained in I was adjustedwith formulation buffer without polysorbate 20. After the addition ofpolysorbate, the solution was filtered through a 0.2 μm filter toproduce a drug substance. The drug substance was aliquoted and stored ina deep freezer (−70±10° C.) until use.

K. Drug Product (Filling, Labeling, Packaging)

The stock stored in a deep freezer was thawed in a water bath maintainedat 28±1° C. and diluted to a protein concentration of about 2.05±0.2mg/mL using formulation buffer (2.25 g/L sodium dihydrogen phosphatemonohydrate, 0.99 g/L sodium hydrogen phosphate heptahydrate, 8 g/Lsodium chloride, 0.23 g/L polysorbate 20, pH 6.0˜7.0). Thereafter, thedilution solution was filtered through a 0.2 μm filter to produce afinal bulk solution. This final bulk solution was filled in 6 mL vialwith approximately 3.3 g using auto filling. Once an vial inspectiontest was passed, the vials were packed to produce a drug product.

The procedure from strain culturing to final product production isillustrated in FIG. 3.

COMPARATIVE EXAMPLE 1 Preparation of ELAPRASE®

ELAPRASE®, commercially available recombinant IDS, was used as acomparative example.

EXPERIMENTAL EXAMPLE 1 Structural Analysis and Characterization ofInventive IDS

<1-1> Amino Acid Sequencing—Internal Sequencing

Deglycosylated IDS was separated by SDS-PAGE, followed by gel slicing.Then, digests resulting from treatment with various endoprotenases(trypsin, chymotrypsin, AspN, chymotrypsin/trypsin, AspN/trypsin, GluCand GluC/trypsin) were analyzed using MALDI-MS/MS and LC-ESI-MS/MS (FIG.5). As a result, a total of 525 amino acid sequences were identified.The amino acid sequences coincided with the theoretical sequence ofhuman IDS (FIG. 6).

<1-2> Disulfide Bond Analysis

In a polypeptide, a disulfide bond is a covalent linkage, usuallyderived by the coupling of two SH groups of cysteine residues, playingan important role in stabilizing the higher structure of proteins.Theoretically, the 525 amino acids of IDS contain six cysteine residues,four of which form disulfide bonds. In this example, the location ofcysteine residues responsible for the disulfide bonds of IDS wasidentified. First, IDS was deglycosylated by treatment with PNGase F toexclude the interference of sugars. In order to prevent the cysteineresidues that do not take part in the formation of disulfide bonds fromacting as an interfering factor, 4-vinylpyridine was used to convert IDSinto a non-reduced sample so that the SH groups are restrained fromrandomly forming S—S bonds. Meanwhile, the disulfide bonds were cleavedby DTT, followed by blocking with 4-vinylpyridine to give a reducedsample. Trypsin and AspN, selected on the result of Experimental Example1-3, were applied to the non-reduced and the reduced sample. The peptidefragments thus obtained were separated by RP-HPLC. RP-HPLC chromatogramsof the non-reduced and the reduced samples were compared so as todiscriminate the peaks that were found in the non-reduced sample, butnot in the reduced sample (FIG. 7).

For more exact analysis, fractions at the discriminated peaks werereduced in size by additional treatment with endoproteinases, and thepeaks containing disulfide bonds were analyzed using MALDI-MS (FIG. 8).

Peaks with disulfide bonds were again sequence analyzed usingMALDI-MS/MS (FIG. 9) to examine the positions of cysteine residues thatform disulfide bonds among the 525 IDS amino acid residues. As shown inFIG. 10, disulfide bonds were observed to form between C146-C159 andbetween C397-C407.

<1-3> Analysis of Formylglycine Content

IDS degrades heparan sulfate and dermatan sulfate, both of which are akind of glycosaminoglycan (GAG). This degradation activity is notacquired until the cysteine residue at position 59 in the active site(Cys59) is converted into formylglycine (FGly) by post-translationalmodification. Thus, the degradation activity of IDS was analyzed byexamining the post-translational modification of Cys59 to FGly. For thisanalysis, AQUA (absolute quantification), a quantitative analysis methodbased on MS (Mass Spectroscopy), was used, in which a radio-labeledsynthetic substrate (AQUA peptide) was spiked into a sample. Toquantitatively analyze formylglycine at Cys59 position, a serialdilution of AQUA peptide was spiked into a sample and a calibrationcurve was drawn. Ratios of FGly-type peptide to Cys-type peptide weremeasured by LC-ESI-MS analysis, and applied to the AQUA calibrationcurve to calculate the content of formylglycine.

This analysis determined the conversion of Cys59 to FGly be a rate of80±15%. In consideration of the Cys59 to FGly conversion rate of about50% in the commercially available agent ELAPRASE® (Elaprase ScienceDiscussion, EMEA, 2007; Genet Med 2006:8(8):465-473), the therapeuticcomposition comprising the IDS of the present invention and theformulation prepared with the composition is anticipated to have muchhigher therapeutic activity compared to ELAPRASE®.

<1-4> Identification of Glycosylation Pattern

An assay was performed to examine whether the IDS of the presentinvention is glycosylated and to identify the glycosylation pattern ifany. To this end, IDS was treated with various glycoside hydrolaseenzymes, the digests were separated on by SDS-PAGE and their motilitypatterns were analyzed.

In detail, IDS samples were digested with combinations of the followingfour glycoside hydrolase enzymes and separated by SDS-PAGE.

TABLE 1 Properties of Sugar Cleaving Enzymes Function/Property PNGase FCleaves a sugar moiety (N-glycan) from protein Asn at the cleavage siteis converted into Asp Endo H Cleaves a sugar moiety (N-glycan) fromprotein unlike PNGase F, Endo H acts on oligosaccharides of high-mannosetype and hybrid type O-Glycosidase Cleaves a sugar moiety (O-glycan)from protein Sialidase Cleaves terminal sialic acid residues of N-glycanor O-glycan

As can be seen in FIG. 11, the IDS of the present invention was cleavedby PNGase F and Endo H, but not by O-glycosidase, indicating that theIDS of the present invention is an N-glycosylated protein. In addition,the IDS was completely cleaved by PNGase F, but its size reduction wasslight upon treatment with Endo H. PNGase F acts on the glycosylationsites of all the three patterns whereas Endo H acts on the glycosylationsites of high-mannose type and hybrid type. Taken together, theseresults indicate that the IDS contains the three glycosylation patternscomplex, high-mannose and hybrid.

<1-5> Analysis of Mannose-6-phosphate Content

Binding to a M6P receptor on cells, mannose-6-phosphate (M6P) allows IDSto be internalized into cells and thus to hydrolyze heparan sulfate ordermatan sulfate in lysosomes. In this Example, IDS was acid hydrolyzedwith trifluoroacetic acid (TFA) and subjected to HPAEC-PAD (Bio-LC) toquantitatively analyze mannose-6-phosphate.

IDS was hydrolyzed with 6.75M TFA and the hydrolysate was analyzed usingliquid chromatography (High Performance Anion-Exchange Chromatographywith Pulsed Amperometric Detection; HPAEC-PAD). M6P concentration ofwhich was already known was analyzed under the same condition, and molarratios of M6P to glycoprotein were obtained by comparison of the areas.Analysis was conducted in triplicate. M6P standard materials and M6Pcomposition chromatograms of the IDS are shown in FIG. 12 and the molarratios of M6P are summarized in Table 2, below.

TABLE 2 Analysis Results for Mannose-6-phosphate content M-6-P AmountAmount Ratio Run Rat. Time pmol/25 μl pmol/25 μl M-6-P/Protein No. (min)M-6-P Protein (mol/mol) 13 11.25 1320.59 428 3.09 14 11.23 1241.31 4282.90 15 11.23 1245.83 428 2.91 AVG 11.24 1269.25 428 2.97 CV 0.09% 3.51%0.11

As is understood from the data of Table 2, there are approximately 3moles of M6P per mole of IDS. From these results, it is inferred thatthe therapeutic composition comprising the IDS of the present inventionand the formulation prepared with the composition have a high ability tocatabolize GAG accumulated in lysosomes.

<1-6> Mass Analysis

Masses of glycosylated IDS and deglycosylated IDS were measured usingMALDI-TOF-MS. Treatment of glycosylated IDS with PNGase F affordeddeglycosylated IDS. MALDI-TOF-MS was performed using Voyager-DE PROBiospectrometry (Applied Biosystems, USA) coupled with a delayedExtraction laser-desorption mass spectrometer. The instrument wasnormalized with bovine serum albumin and IgG1. Analysis results aresummarized in Table 3, below.

TABLE 3 MALDI-TOF-MSMALDI-TOF-MS Analysis Results of IDS m/z charge(z)Protein Mass(Da) remark Glycosylated IDS 25646 3 76935 38708 2 7741477360 1 77359 154533  1 77266 dimer Average 77244 ± 210 DeglycosylatedIDS 29767 2 59532 34655 PNGase F 59313 1 59312 118706  1 59353 dimerAverage 59399 ± 120 Sample Molecular Weight Theoretical 59298 DaGlycosylated 77244 ± 210 Da Deglycosylated 59399 ± 120 Da

As apparent from the data of Table 3, the molecular size is 77,244 Dafor glycosylated IDS and 59,399 Da for deglycosylated IDS, which issimilar to the molecular weight calculated on the basis of the aminoacid sequence, which is 59,298 Da.

<1-7> Purity Measurement

The purity of IDS was measured using size exclusion chromatography. Sizeexclusion chromatography is a chromatographic method in which moleculesin solution are separated by their relative molecular weight and shape.In size exclusion chromatography, proteins larger than the pore size ofthe column cannot penetrate the pore system and pass through the columnat once. Subsequently, the analytes with smaller molecular weights orsizes elute later. For this chromatography, Alliance 2695 HPLC system(Waters, Wis., USA) coupled with 2487 UV/VIS detector (Waters, Wis.,USA) was employed. Proteins were detected at 214 nm, and analyzed usingEmpower 2 Software. The analytes were loaded onto a TSK G3000SWXL columnlinked to a TSK SWXL guard column (Tosoh, Japan). IDS, after beingdiluted to a concentration of 1.0 mg/mL in a formulation buffer, wasloaded in a volume of 10 μL onto the column. They were allowed to flowwith mobile phase (20 mM sodium phosphate buffer, 200 mM NaCl, pH 7.0)at a flow rate of 0.5 mL/min for 60 min.

Analysis results are shown in FIG. 13. As can be seen, IDS monomers hada retention time of approximately 16.4 min, and were eluted with 100%purity.

<1-8> Activity Measurement Using Synthetic Substrate

The reaction of IDS with the synthetic substrate(4-methylumbelliferyl-L-iduronide-2-sulfate Na₂ (MU-IdoA-2S) for 4 hoursreleases the sulfate moiety (primary reaction). After the primaryreaction, the addition of LEBT (lysosomal enzymes purified from bovinetestes) induces a secondary enzymatic reaction with the substrate4-methylumbellifery-L-iduronide (reactant left after the release of thesulfate moiety in the primary reaction) to separate the4-methylumbelliferyl moiety from the L-iduronide moiety. Because theremaining 4-methylumbelliferyl is fluorogenic, the activity of IDS wasevaluated by measuring the intensity of fluorescence (Ex.355 nm/Em.460nm). The IDS of the present invention was found to range in specificactivity from 19 to 55 nmol/min/μg. This activity indicates thatformylglycine exists in the active site of the enzyme as a result of thepost-translational modification of the cysteine residue at position 59in IDS.

<1-9> Activity Measurement Using Natural Substrate

In order to determine whether the reaction with the IDS and naturalsubstrate, the sulfate ions released from the substrate (heparindisaccharide) by reaction with IDS were measured. The reaction mixturewas loaded onto an ion column (Vydac 302IC) and allowed to flow with themobile phase of 0.49 g/L phthalic acid at a flow rate of 2 ml/min,during which free sulfate ions were detected at 290 nm in negative mode.

As shown in FIG. 14, the IDS was confirmed to hydrolyze sulfate ion fromheparin disaccharide, indicating that the IDS is capable of degradingO-linked sulfate of dermatan sulfate and heparan sulfate in vivo.

<1-10> In vivo Cellular Uptake Activity

The cellular internalization activity of the IDS was measured using thenormal fibroblast cells and Hunter syndrome patient cells. In thisregard, normal fibroblast cells and Hunter syndrome patient cells(obtained from Samsung Medical Center, Seoul, Korea) were cultured andallowed to be internalized into cells while they were incubated withvarious concentrations of IDS at 37° C. for 20 hours in a 5% CO₂incubator. After being harvested, the cells were lyzed, and the level ofthe IDS internalized into the cells was determined in the lysate.

On the basis of the concentration ratio of internalized IDS to IDS addedto the normal fibroblast cells, a Michaelis-Menten graph and aLineweaver-Burk plot were constructed from which K_(uptake) (IDSconcentration at which the reaction rate is half of the maximum rateachieved at saturating substrate concentrations) was calculated.K_(uptake) was calculated to be 18.0 nM or less, indicating that IDS isinternalized into cells by the binding of the M6P of IDS to M6Preceptors on the cell surface (FIG. 15).

Also, the cellular uptake and activity of IDS in Hunter syndrome patientcells as well as normal human fibroblast cells were analyzed. The uptakeand activity of the IDS were increased in both the cells, demonstratingthat the IDS of the present invention is more efficiently internalizedinto cells (FIG. 16).

EXPERIMENTAL EXAMPLE 2 Clinical Analysis for Effect of IDS

Thirty one patients with Hunter syndrome were divided into three groups,administered with the IDS of the present invention and analyzed forparameters associated with Hunter syndrome. ELAPRASE®, a commerciallyavailable therapeutic agent for Hunter syndrome, was used as a positivecontrol.

<2-1> Change in Urine GAG Level (Primary Check Parameter for ValidityTest)

The three groups of Hunter syndrome patients were administered for 24weeks with ELAPRASE® (0.5 mg/kg) and the IDS of the present invention(0.5 mg/kg and 1.0 mg/kg), and urine GAG (Glycosaminoglycan) levels weremeasured as reported previously (Conn. Tissue Res. Vol. 28, pp 317-324,1990; Ann. Clin. Biochem. Vol. 31, pp 147-152, 1994). Measurements aresummarized in Table 4, below.

TABLE 4 Change in Urine GAG Level with IDS Administration ELAPRASE ®Inventive IDS Inventive IDS Group (0.5 mg/kg) (0.5 mg/kg) (1.0 mg/kg)Change in urine −18.7 −29.5 −41.1 GAG level (%)In Hunter syndrome patients, as shown in Table 4, urine GAG levels weredecreased by 18.7% upon the injection of ELAPRASE®, but by 29.5% uponthe injection of the IDS of the present invention at the same dose. Inaddition, when injected at a dose of 1.0 mg/kg, the IDS of the presentinvention reduced the urine GAG level by as much as 41.1%. These resultsdemonstrate that the IDS of the present invention is effectivelytherapeutic for Hunter syndrome, a disease caused as a result of theaccumulation of GAG.

<2-2>6-MWT (6 Minute Walking Test) Change (Secondary Checking Parameterfor Validity Test)

After Hunter syndrome patients were administered with ELAPRASE® and theIDS of the present invention for 24 weeks, the distances which theywalked for 6 minutes were measured according to the method described inAM. J. Respir. Crit. Care. Med., Vol 166, pp 111-117, 2002. The resultsare given in Table 5, below.

TABLE 5 6-MWT Test Results ELAPRASE ® Inventive IDS Inventive IDS Group(0.5 mg/kg) (0.5 mg/kg) (1.0 mg/kg) 6-MWT Distance 5.9 67.6 52.8 (m)6-MWT Change 1.3 18.2 13.4 (%)

As shown in Table 5, the 6-WMT change was merely 1.3% for the patientsadministered with ELAPRASE®, but increased to 18.2% for the patientsadministered with the same dose of the IDS of the present invention.Hunter syndrome patients have trouble walking due to contracture.However, the IDS of the present invention improves the symptoms and thusis effective for the treatment of Hunter syndrome.

What is claimed is:
 1. A method for treating Hunter syndrome in asubject in need thereof, the method comprising administering to saidsubject a composition comprising the effective amount of a recombinantiduronate-2-sulfatase (IDS) having the amino acid sequence of SEQ ID NO:1, wherein a cysteine residue at position 59 in the IDS amino acidsequence in the composition is converted into formylglycine (FGly) at amolar ratio of 65% or higher.
 2. The method of claim 1, wherein thecysteine residue at position 59 in the recombinant IDS amino acidsequence is converted into FGly at a molar ratio of 75% or higher. 3.The method of claim 1, wherein the cysteine residue at position 59 inthe recombinant IDS amino acid sequence is converted into FGly at amolar ratio of 80% or higher.
 4. The method of claim 1, wherein therecombinant IDS contains mannose-6-phosphate in an amount of 2.0 to 4.0moles per mole of IDS.
 5. The method of claim 4, wherein the recombinantIDS contains mannose-6-phosphate in an amount of 2.5 to 3.0 moles permole of IDS.
 6. The method of claim 1, wherein the composition issuitable for injection, oral administration, or parenteraladministration.
 7. A method for treating Hunter syndrome in a subject inneed thereof, the method comprising administering to said subject aninjectable formulation comprising a recombinant iduronate-2-sulfatase(IDS) at a dose of 0.5-1 mg IDS/kg body weight, said recombinant IDShaving the amino acid sequence of SEQ ID NO: 1, wherein a cysteineresidue at position 59 in the IDS amino acid sequence is converted intoformylglycine (FGly) at a molar ratio of 65% or higher.
 8. The method ofclaim 7, wherein the cysteine residue at position 59 in the recombinantIDS amino acid sequence is converted into FGly at a molar ratio of 75%or higher.
 9. The method of claim 7, wherein the cysteine residue atposition 59 in the recombinant IDS amino acid sequence is converted intoFGly at a molar ratio of 80% or higher.
 10. The method of claim 7,wherein the dose is about 0.5 mg IDS/kg body weight.
 11. The method ofclaim 7, wherein the dose is about 1 mg IDS/kg body weight.
 12. Themethod of claim 7, wherein the formulation is administeredintravenously.
 13. The method of claim 7, wherein the formulation isadministered subcutaneously.
 14. The method of claim 1, wherein theeffective amount of the IDS is 0.5 mg IDS/kg body weight.
 15. The methodof claim 1, wherein the effective amount of the IDS is 1.0 mg IDS/kgbody weight.
 16. The method of claim 7, wherein the recombinant IDScontains mannose-6-phosphate in an amount of 2.0 to 4.0 moles per moleof IDS.
 17. The method of claim 16, wherein the recombinant IDS containsmannose-6-phosphate in an amount of 2.5 to 3.0 moles per mole of IDS.